Motor compressor



Oct. 8, 1935. R. P. PESCARA 2,016,613

MOTOR COMPRESSOR Filed Jan. 5, 1933 Ram Bateras Descara I ATTO EY Patented Oct. 8, 1935 Z,0l6,6l3 I PATENT OFFICE 2.016.613 moron oomnsson Raul Patent Pescara, Paris, France Application January 5, 1933, Serial No. 650,352

In Germany June 6, 1932 4 Claims. (01. 230-56) The present invention relates to motor compressors of the type in which two opposed compressing pistons are driven directly by internal combustion of a fuel.

In apparatus of that type, the inner ends of the pistons reciprocate in a motor cylinderinto which the fuel is injected and in which it is subsequently ignited. The outer ends of the pistons lit in a fluid-tight manner in two compression cylinders respectively disposed on eitherside of said motor cylinder coaxially therewith. The return stroke or instroke of the pistons is caused by the expansion of the air cushions that remain in the clearance spaces of said compression cylinders at the end of the outstroke.

The chief object of the'present invention is to provide a motor compressor of the type above referred to in which the work of said air cushions is substantially constant in spite of variations in the conditions of work of the machine, that is for variable delivery pressures, and for different lengths of stroke of the pistons.

. According to the present invention, I obtain this result by varying the amount of fuel fed to the motor cylinder in accordance with variations of pressure in the delivery pipe of the compressor. In a preferred form of my invention, I provide means, either automatic or manual, for throt fling the delivery pipe of the compressor so as to produce a temporary increase of pressure in said pipe, and means, responsive to variations of said pressure, for varying the amount of fuel fed to the motor cylinder.

A preferred embodiment of my invention will be hereinafter described with reference to the accompanying drawing, given merely by way of example, and in which:

Fig. 1 is a longitudinal sectional view of a motor compressor according to my invention;

Fig. 2 is a diagram illustrating the operation of the motor compressor. The motor compressors with which the invention is concerned are of the type shown in Fig. 1. A compressor of that type comprises two opposed pistons ll and I2 the inner ends of which reciprocate in a common motor cylinder l3. The outer ends of said pistons reciprocate in compression cylinders I4 and I5 respectively connected with delivery pipe 24 through valves 23 or any other suitable means. The two pistons are interconnected through rods such as It and a crank 18 journalled on shaft I! so that the movements of said pistons are synchronized.

The inlet and outlet ports, I 9 and 20 respecttively, of the motor cylinder are uncovered by the pistons. The fuel is fed into said motor cylinder in the middle part thereof through a pump 45 the feed of which is controlled through rods M, 40, 39 and rack and pinion 43. The air to be compressed is admitted into the compression 5 chambers through valves 2| provided in the pistons or through any other equivalent means.

The operation of a motor compressor of that type is illustrated in Fig. 2 in which the pressures in the compression chamber of one cylinder are 10 plotted in ordinates and the displacements of the corresponding piston are plotted in abscissas. For a given delivery pressure, corresponding to EC for instance, the outstroke is represented by portion ABC of the curve and the instroke'corresponds to portion CDA of the curve. During a portion (AB) of the outstroke, the air is adiabatically compressed in the compression chamber,

say l5, of one cylinder. When the pressure of said air has been raised to a value equal to the delivery pressure, that is to the pressure in delivery pipe 24, valves 23 open and the air is discharged through said valves at a uniform pressure (portion BC of the curve). At the end of the outstroke, valves 23 close and the cushion of 25 air remaining in the clearance space of the cylinder expands adiabatically (portion CD of the curve) thus producing the instroke of the piston. When the pressure in the cylinder is equal to the atmospheric pressure, air is admitted into said cylinder through valves 2|, the pressure remaining equal to the atmospheric pressure.

Now it is known that the work of the air cushion remaining in the clearance space of the cylinder for producing the instroke of the piston is proportional with area CDE. On the other hand it will readily be understood that said area depends on both the ordinate of horizontal line BC, which is determined by the delivery pressure, and the length of said line BC, which is determinedby the quantity of fuel fed to motor cylinder l3. It follows that, by varying the amount of fuel fed to cylinder l3 in accordance with the variations of the delivery pressure, other diagrams of operation, such as AFGHA and AKLMA, can be obtained for which areas GHJ or LMN are equal to area CDE. In other words, the diagrams of Fig. 2 show that, by suitably varying the feed of the fuel in accordance with the variations of the delivery pressure it is possible to obtain substantially constant operation of the air cushions that produce the instroke.

A preferred embodiment of a device for performing such a compensating regulation is shown in Fig. l. The air discharged to a reservoir through pipes 24, 25 and 28 has to flow past a portion of restricted section in which a needle 21 can be more or'less engaged. Said needle 21 is carried by a piston 29 adapted to slide in a cylinder 3| connected with pipe 25 through a conduit 32. One face of said piston 29 is therefore subjected to the delivery pressure of the compressor, while the other face is subjected to the action of a spring 30 hearing against a plate 33. The position of said plate 33 can be controlled through a bell crank 34 and a rod 35. If it is desired that the control of the compressor should be automatic, for instance if it is desired that an engine driven by the compressed air from the compressor should run at a uniform speed of revolution, rod 35 is controlled by a governor ll fitted on said engine.

On the other hand, the feed of the injection pump of the motor cylinder is controlled by rod 4|, bell crank lever 40 and rod 39, which is carried by piston 31. Said piston is adapted to reciprocate in a cylinder 36 one end of which is connected through conduit 42 with pipe 25. One face of the piston 31 is therefore subjected to the delivery pressure, while the other face is subjected to the action of a spring 38 acting in the opposite direction.

The operation of the device is as follows:

Supposing for instance that governor 44 is connected to an engine driven by the compressed air from the compressor, if said engine requires an increased rate of feed of said compressed air, the governor pushes rod 35 in an upward direction, which causes piston 29 to move in cylinder 3| and needle 21 to further engage into the restricted portion 26 of pipe 25. The pressure increases in pipe 25. This causes piston 31 to move upwardly and to act, through members 39, 40, 4|, on the injection pump in such manner as to increase the feed thereof. Furthermore, the increased pressure in pipe 25, transmitted to cylinder 3| through pipe 32, pushes piston 29 and consequently needle I, back to a position that corresponds to an equilibrium between the pressure in pipe 25, which corresponds to the power delivered by the compressor, and the thrust exerted by the governor on the opposite face of piston 29, which corresponds to the power absorbed by the engine above referred to.

Of course, rod 35 might as well be actuated manually in order to vary the delivery pressure, that is the power delivered by the compressor, while maintaining under all circumstances a correct return stroke of the pistons.

When rod 35 is displaced manually, the machine (for instance a turbine) or the device driven by the compressed air from the compressor may be so arranged that they do not require any other regulating device, and supply an amount of. work in accordance with the value of the delivery pressure of the motor compressor.

Attention is called to-the fact that, with such a regulation device, which involves considerable variations in the stroke of the pistons, the inlet and outlet ports l9 and 20 should be made of a sufiiciently elongated shape.

While I have described what I deem to be a practical and efllcient embodiment of my invenvention, it should be well understood that I do not wish to be limited thereto as there might be changes made in the arrangement, disposition 5 and form of the parts without departing from the principle of my invention as comprehended within the scope of the appended claims.

What I claim is:

1. In a motor compressor including a motor 10 cylinder, two compression cylinders disposed on opposite sides thereof and coaxially therewith, two opposed pistons the inner ends of which reciprocate in the motor cylinder and the outer ends of which reciprocate in the-compression cylinders respectively, and a delivery pipe connected with at least one of said compression cylinders, the combination of means, responsive to variations of pressure in said pipe, for regulating the feed of fuel to said motor cylinder, and means 20 for throttling said delivery pipe.

2. In a motor compressor including a. motor cylinder, two compression cylinders disposed on opposite sides thereof and coaxially therewith, two opposed pistons the innerends of both of 35 which reciprocate in the motor cylinder and the outer ends of which reciprocate in the compression cylinders respectively, and a delivery pipe connected with at least one of said compression cylinders, the combination of means, responsive to variations of pressure in said pipe for regulating the feed of fuel to the motor cylinder, adjust-, able yielding means, responsive to the action of said pressure, for throttling said delivery pipe, and means for adjusting said yielding means.

3. In a motor compressor including a motor cylinder, two compression cylinders disposed on opposite sides of said motor cylinder and coaxially therewith and two opposed pistons the inner ends of both of which reciprocate in the 40; motor cylinder and the outer ends of which reciprocate in the compression cylinders respectively, the combination of a delivery pipe connected with at least one of said compression cylinders, and having a portion of restricted sec-45; tion, means, responsive to variations of pressure in said pipe, for regulating the feed of fuel to the motor cylinder, at tapering organ in said pipe adapted to engage more or less in'the portion of restricted section of said pipe, a cylinder, a piston 50 fitting slidably in the last mentioned cylinder, means for connecting one end of said last mentioned cylinder with said delivery pipe, a spring acting on said piston so as to urge it in the opposite direction, and means for adjusting the action 65 of said spring.

4. A device according to claim 3 in which the first mentioned means, for regulating the feed of fuel to the motor cylinder include a stationary cylinder, a piston adapted to move with a fluid- 6Q 

